The present invention relates to an expansion valve and a refrigeration cycle for use in an air conditioner of a car, a refrigerating display case, or the like.
There are various types of expansion valves, and a widely used expansion valve comprises an orifice formed by narrowing a portion of a high-pressure refrigerant path through which high-pressure refrigerant traveling to an evaporator passes, and a valve member disposed upstream of and opposing to the orifice, the valve member moved to open and close the valve in response to the temperature and pressure of a low-pressure refrigerant sent out from the evaporator.
One example of this type of expansion valves is disclosed in Japanese Patent Laid-Open No. 8-334280 regarding an expansion valve used in a refrigeration cycle of an air conditioner of a car.
That is, as illustrated in FIG. 3, a refrigeration cycle 1 comprises a compressor 2 driven by an engine, a condenser 3 connected to the output side of the compressor 2, a liquid tank 4 connected to the condenser, an expansion valve 5 for expanding the liquid-phase refrigerant from the liquid tank 4 into a two-phase refrigerant of vapor and liquid, and an evaporator 6 connected to the expansion valve 5.
The expansion valve 5 comprises an expansion valve body 5a provided with a high-pressure-side path 5b through which liquid-phase refrigerant travels and a low-pressure-side path 5c through which two-phase refrigerant of vapor and liquid travels, wherein the high-pressure-side path 5b and the low-pressure-side path 5c are communicated via an orifice 7. Further, a valve member 8 that adjusts the amount of refrigerant passing through the orifice 7 is equipped in a valve chamber 8d. 
In the expansion valve 5, a low-pressure refrigerant path 5d is formed to pass through the expansion valve body 5a, and in the low-pressure refrigerant path 5a is disposed an actuating rod 9a in a slidable manner, the actuating rod 9a being driven by a power element portion 9 fixed to the upper portion of the expansion valve body 5a. The interior space of the power element portion 9 is divided by a diaphragm 9d into an upper airtight chamber 9c and a lower airtight chamber 9cxe2x80x2. A disc portion 9e disposed at the upper end of the actuating rod 9a comes into contact with the diaphragm 9d. In the power element portion 9, an upper lid 9f is provided with a tube connecting hole 9g formed to the center portion thereof, and a capillary tube 9h is mounted to the tube connecting hole 9g. 
Furthermore, at the lower portion of the expansion valve body 5a, a compression coil spring 8a pressurizing via a support member 8c the valve member 8 toward its valve closing direction is disposed within the valve chamber 8d. The valve chamber 8d is defined by the expansion valve body 5a and an adjustment screw 8b screwed onto the expansion valve body 5a through the seal of an O-ring 8e. An actuating rod 9b attached to the lower end of the actuating rod 9a moves the valve member 8 toward the valve opening direction by the sliding movement of the actuating rod 9a. 
The actuating rod 9a in the power element portion 9 transmits the temperature of the low-pressure refrigerant path 5d to the upper airtight chamber 9c, and in correspondence to the transmitted temperature, the pressure within the upper airtight chamber 9c changes. For example, if the temperature is high, the pressure within the upper airtight chamber 9c rises so that the diaphragm 9d pushes down the actuating rod 9a, the movement of which drives the valve member 8 in the direction opening the valve. Thus, the amount of refrigerant passing through the orifice 7 increases, and the temperature of the evaporator 6 is thereby reduced.
On the other hand, if the temperature is low, the pressure within the upper airtight chamber 9c falls so that the force of the diaphragm 9d pushing down the actuating rod 9a weakens, and the valve member 8 moves in the direction closing the valve by the force of the compression coil spring 8a biasing the member 8 in the valve closing direction. Thus, the amount of refrigerant passing through the orifice 7 decreases, and the temperature of the evaporator 6 is thereby increased.
Thus, the expansion valve 5 moves the valve member 8 according to the change in temperature of the low-pressure refrigerant path 5d to thereby change the opening of the orifice 7, adjusting the amount of refrigerant passing through the orifice and thus controlling the temperature of the evaporator 6. Thus, in this type of expansion valve 5, the opening area of the orifice 7 for realizing adiabatic expansion of the liquid-phase refrigerant to two-phase refrigerant is determined by adjusting via the adjustment screw 8b the spring load of the compression coil spring 8a having a variable spring load that pressurizes the valve member 8 toward the direction closing the valve.
FIG. 3 illustrates an example of the expansion valve 5 wherein a capillary tube 9h is mounted on the tube mounting hole 9g of the power element portion 9. FIG. 4 illustrates an alternative example comprising a sealing plug 9i provided instead of the capillary tube 9h on the tube mounting hole 9g, an expansion valve body 5a having a rectangular column form, a thin portion 5e formed at the bottom of both side portions of the body, and bolt holes 5f created to the body near the low-pressure refrigerant passage 5d. 
FIG. 5 is a vertical cross-sectional view showing another prior-art example of the expansion valve illustrated with a refrigerant cycle 1, with the construction of the heat sensing shaft varied from the example shown in FIG. 3. An expansion valve 101 illustrated in FIG. 5 comprises a valve body 30 similar to the valve body of the prior art example illustrated in FIG. 3, having a high-pressure-side path 32c through which high-pressure refrigerant flowing toward an evaporator 6 travels, a low-pressure-side path 32b, an orifice 32a disposed between the paths 32c and 32b, a spherical valve member 32d disposed to oppose to the orifice 32a from the upstream side of the refrigerant, a bias means 32e for biasing the valve member toward the orifice from the upstream side, a valve component 32f disposed between the bias means and the valve member for transmitting the biasing force of the bias means to the valve member 32d, a power element portion 36 that operates in connection with the temperature of a low-pressure refrigerant exiting the evaporator 6, and a heat sensing drive rod 318 having a heat sensing rod and an actuating rod integrally formed and disposed between the power element portion and the valve member, wherein the movement of the power element portion 36 drives the valve member 32d to move toward or away from the orifice 32a to thereby control the flow of refrigerant passing through the orifice.
The power element portion 36 comprises a diaphragm 36a made of a metallic thin plate having flexibility such as stainless steel, an upper cover 36d and a lower cover 36h made of stainless steel constituting an airtight wall sandwiching the diaphragm 36a and defining two pressure chambers, an upper pressure chamber 36b and a lower pressure chamber 36c, divided by the diaphragm 36a, and a hole cap 36i for filling a refrigerant into the upper pressure chamber 36b as a diaphragm driving medium. The lower pressure chamber 36c is communicated to a second path 34 via a pressure equalizing hole 36e which is formed concentrically with the center line of the orifice 32a. A refrigerant vapor exiting the evaporator 6 travels through the second path 34, by which the path 34 functions as a gas-phase refrigerant path, and the pressure of the gas-phase refrigerant is loaded on the lower pressure chamber 36c through the pressure equalizing hole 36e. The lower cover 36h is further equipped with a tube-like mounting seat 362, which is screwed onto the valve body 30 via a screw hole 361.
The heat sensing drive rod 318 has a separately formed upper end portion 36k, the heat sensing rod being formed integrally with the actuating rod as a thin rod portion 316 made of stainless steel. The upper end portion 36k is a receiver portion constructed of a stopper portion 312 coming into contact with the lower surface of the diaphragm 36a and having a rim that is enlarged toward the radial direction, and a large-diameter portion 314 slidably disposed within the lower pressure chamber 36c and having on the end opposite from the stopper portion a projection 315 formed to the center thereof. The upper end of the rod 316 is fit to the inner side of the projection 315 formed to the large-diameter portion 314, and the lower end thereof comes into contact with the valve member 32d. 
The rod member 316 constituting the heat sensing rod is driven to slide freely along with the displacement of the diaphragm 36a of the power element portion 36 traversing the path 34, so a clearance (gap) communicating the path 32c and the low-pressure refrigerant path 34 is formed along the rod portion 316. In order to prevent communication through this clearance, an O-ring 40 is disposed on the outer periphery of the rod member 316 within a hole 38, so that the O-ring 40 exists between the two paths.
Reference numeral 35 denotes a valve chamber formed coaxially with the orifice 32a that communicates with the high-pressure-side path 32b and sealed by a plug 39, and further communicates with the high-pressure-side path 32c through the orifice 32a. 
R11 (CCl3F), R12 (CCl2F2) and other conventional flon-group materials have been used as refrigerants in a refrigerating cycle. However, these materials in which all hydrogen atoms of hydrocarbon radicals have been replaced by chlorine-containing halogen are subjected to a worldwide restraint to stop the destruction of the ozone layer in the stratosphere. To provide alternate flon-group refrigerants that will not destruct the ozone layer, hydrogen-containing halogenated hydrocarbon refrigerants, such as R22 (CHClF2), R123 (CF3CHCl2), R111b (CCl2FCH3), R134a (CF3CH2F), and R152a (COOF2CH3), have been developed. Especially among them, non-chlorinated halogenated hydrocarbon, such as R134a (CF3CH2F) and R152a (CHF2CH3), are considered hopeful.
Non-chlorinated halogenated hydrocarbon, however, is inferior to conventional flon-group refrigerants in respect of lubricity, and often causes metallic powder to mix in the refrigerant. Since the expansion valve, among various elements of a refrigeration cycle, comprises a valve member opening and shutting an orifice, the valve seat of the orifice is subjected to local abrasion or a sort of corrosion called erosion by metallic powder or other particles contained in the refrigerant.
Japanese Patent Laid-Open Publication No. 8-334280 discloses a construction in which a metal material harder than the valve body is fixed to the orifice of a valve body of a prior art expansion valve.
In the above-mentioned prior art construction, in fixing the metal material constituting an orifice member to the orifice of the expansion valve, the orifice member is provided with a tapered projection, enabling an edge-seal process for securing the fixing of the member to position.
However, in case the valve body of the expansion valve as illustrated in FIG. 3 is made of aluminum material and the aluminum valve body is anodized to create an anodized aluminum film, the above-mentioned projection may partially crack the anodized aluminum coating of the valve body, making it impossible for the anodized aluminum coating to maintain its anti-corrosion property.
The present invention aims at solving the problems of the prior art. The object of the present invention is to provide an expansion valve having an anodizing treatment provided to the valve body, wherein the valve seat of the orifice is free from local abrasion or corrosion such as erosion.
According to the present invention, there is provided an expansion valve comprising: a valve body including a high-pressure-side path, a low-pressure-side path and a valve opening communicating said two paths; a valve member disposed so as to oppose to said valve opening; and a diaphragm for moving said valve member via an actuating rod; wherein said valve body receives an aluminum anodization treatment, and said orifice is equipped with an orifice member harder than the valve body and having a flat contact surface that comes into planar contact with said valve body.
According to this construction, the anodized aluminum film of the valve body of the expansion valve is free from cracks and damages, and thereby the valve seat of the orifice is protected against local abrasion or erosion.
Furthermore, there is provided an expansion valve wherein the orifice member is a substantially cylindrical member, comprising one open end constituting the flat contact surface that comes into planar contact with the valve body, another open end constituting a surface to which is opposed the valve member, and a screw portion formed to an outer side portion thereof by which the orifice member is fixed to the valve body.
According to this construction, the orifice member capable of preventing local abrasion or erosion can be fixed easily to the valve seat without damaging the anodized aluminum film of the valve body.
There is also provided an expansion valve having an adhesive applied to the screw portion.
Thus, the orifice member can be fixed to the valve seat securely for a long period of time.
Furthermore, there is provided a refrigeration cycle comprising a compressor, a condenser for condensing a gaseous refrigerant heated and compressed by the compressor, a liquid tank for separating the condensed refrigerant into vapor and liquid and for removing moisture and dust from the refrigerant, an expansion valve for expanding the refrigerant from the liquid tank, and an evaporator for realizing heat-exchange between the refrigerant and air, the components all connected by a piping; wherein the refrigerant is non-chlorinated halogenated hydrocarbon, and the expansion valve is any of the expansion valves constructed as explained above.
According to this system, even if the refrigeration cycle utilizes non-chlorinated halogenated hydrocarbon as refrigerant, the anodized aluminum film of the expansion valve is free from cracks, the valve seat of the expansion valve is protected against local abrasion or erosion, and thus a refrigeration cycle capable of operating stably for a long period of time is provided.